From my own experience of dealing with names in the C19 and C20 there was a tendency to anglicise names for example the Romanian name Iuliu would be rendered as Julius or Julian in books published in the UK.

Alternatively, it could be an issue with orthography and the o being read as an a and the mistake being repeated.

Edit - he is sometimes F.J. and others F.I so perhaps the name was difficult to read?

I've read (in which book I can't remember), that the inventor was a Doncaster Works employee, Henry Cortazzi. Apparently his name was Anglicised into Cartazzi, and this is the name the man himself went by. When I get chance, I'll dig out the reference and quote it.

I’ve heard his name pronounced with an ‘O’ at A1 Trust meetings in recent years.

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I've found the reference I was looking for: East Coast Pacifics at Work (P.N. Townend), p. 17

"Great Northern was however fitted with a simple and light arrangement devised by Cortazzi, at one time employed at Doncaster under Sturrock, and later Superintendent of the GIP Railway in India from 1866. His name over the years has been varied to Cartazzi, the name by which the design of the truck is usually known but whether he invented the arrangement or his predecessor on the GIP Railway who devised a system of inclined planes used in a similar manner is in doubt".